I have installed Geno's Muffler Eliminator pipes on two trucks so far and they sound great. Louder than stock with more of that "Big Rig" sound, but not too loud. Fit was excellent and installation was a breeze. But if I had to do it again, I would just replace the muffler and resonator(I'm saying resonator assuming that you have a 24-valve Cummins) with just a straight section of 3" pipe. Less money and just as easy to install.
Best Of Luck
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1999 2500 Reg. Cab, Sport, 4x4, 24-Valve Cummins(Of Course), Auto, 3:54 LSD, Flame Red/Agate, K&N Air Filter, TST PowerMax1(Original),Straight Piped, DD Stage 3's, Bill K's Valve Body (TC Next), Pillar Mount Pyro/Boost, Xenon Fender Flares, M/T 16x8 Classics, 285 BFG's...
1930 Ford Model "A" Coupe, 327 Chevy ,Muncie 4-spd, Ford 9" Rear w/4:11 Posi, Mustang II Front, All Steel...
1969 Camaro 355 w/Nitrous, 350 Turbo, 4:56 Posi, Hugger Orange w/White Houndstooth Int...
1998 Ski-Doo Mach Z, B&B Eliminator Silencer, V-Force Delta Reeds, 192 Top Gun Studs...